Supplied air respirators are regularly worn in environments where the surrounding air contains or may contain contaminants. Clean air is delivered to the wearer from a supply tank or from a powered air source that drives or draws ambient air through an air filter.
Systems that use a powered air source to supply clean air to the wearer are referred to as powered air purifying respirators, or “PAPRs”. PAPRs may come in a variety of types, but two common types are belt pack PAPRs and helmet PAPRs. Belt pack PAPRs typically have two main parts: a facepiece and a filtering unit. The facepiece is worn at least over the nose and mouth of the user (it also may cover the eyes and ears), and the filtering unit is worn about the user's waist. Typically a hose connects the filtering unit to the facepiece. Helmet PAPRs typically include a pivotal visor as a facepiece and a filtering unit contained within or attached to the helmet.
In both types of PAPRs, the filtering unit often includes one or more filter cartridges, a housing, a fan, and an electric motor that drives the fan. The fan and motor are contained within the housing, and the filter cartridges are attached to the housing body. Ambient air is filtered by being drawn through filter elements that are contained within the filter cartridges. The electrically powered fan drives or draws the air through the filter cartridges, through the hose, and into the facepiece interior. Because the fan does the work required for air movement through the PAPR system, the user is able to comfortably receive a clean supply of air with little effort.
Each style of PAPR has advantages and disadvantages. The belt pack style can be easier for a user to wear because the weight of the filtering unit is carried on the waist and not the head. However, having a two piece system can be cumbersome and the connecting hose can interfere with the free movement of the user and also is at risk of becoming tangled, ruptured or even detached. The helmet style PAPR avoids these drawbacks by being a single self-contained unit, but the weight of the filtering unit can be uncomfortable especially when worn for long periods of time.